Minimal size and a minimal number of external terminals or pins are important performance measures for integrated audio amplification circuits for application in miniature capacitor or condenser microphones such as ECM and MEMS condenser microphones. These types of condenser microphones are designed for capture and processing of sound in numerous portable devices and applications such as mobile terminals, personal computers, hearing instruments, headsets, sound recording cameras etc. These miniature condenser microphones typically provide very limited housing space for accommodating integrated audio amplification circuits.
Furthermore, these applications are normally cost sensitive. Since manufacturing costs of an integrated semiconductor circuit are largely proportional to the size of the integrated circuit, there is a considerable advantage in minimizing the number of pads or terminals of the integrated circuit due to the associated die area consumption. Likewise, simplification of audio signal processing and data communication interface circuitry of the integrated audio amplification circuit is also of considerable interest because this reduces die area consumption and therefore manufacturing costs as well. The data communication interface circuitry may comprise a programming interface allowing an external application processor, like a general purpose microprocessor or Digital Signal Processor, to set or modify programmable configuration settings of a signal processor or an audio output format of the integrated audio amplification circuit. The programming interface allows the external application processor to control operational characteristics of the integrated audio amplification circuit by changing the programmable configuration setting and adapt the operational characteristics to requirements of a particular application or a particular operational state, e.g. a power down state.
Furthermore, there is a continued increase in the number of microphones utilized in the portable devices. The application of multiple microphones is advantageous to support various types of sophisticated audio signal processing like stereo sound recording, beam-forming, wind noise cancellation etc. However, the use of multiple microphones in portable devices tend to increase the number of external data input/output terminals, increase the amount of data wiring, increase the complexity of data transmission and receiving interfaces, increase complexity of associated data protocols etc. This is generally undesirable because these factors tend to increase the size and manufacturing costs of both the integrated audio amplification circuits and the portable device in which the circuits are incorporated.